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tv   Sean Carroll Something Deeply Hidden  CSPAN  October 9, 2019 10:57pm-12:23am EDT

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>> good evening everybody. hello. thank you for coming out to bring scientist of all disciplines and then to interact directly with them
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and with those discoveries and here in brooklyn but speaker from new york science secret club north and and then right behind the new republic as always. and with rebecca and mary for helping us and also zach. and then fabulous libation of money and exhibit a.
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and you could get it at the bar to the left now is a good time to do it. and then to be back on decemberd with astronaut catherine sullivan a former nasa astronaut the first woman to walk in space but also because of an oaa very timely. so if you would like to find out in our upcoming events check out our website we have blogspot website and you can sign up for the mailing list
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they are. so tonight theoretical physicist has a new book out and in fact it came out today. it came out today. . . . . physicist, mathematician, professor at columbia university and director of the center for theoretical physics is also a
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playwright and sometimes an actor and a best-selling author of several science books including the elegant universe and fabric of the cosmos and he is hosted to any award-winning pbs series based on his book and is also the founder of the gold old festival please welcome doctor brian greene. [applause] [cheering] thank you very much. the quantum cocktail so tonight's focus is on quantum mechanics and as i think many of you know in a truly early years of the 20th century, we had a
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wonderful quite straightforward understanding of the universe. classical physics. beginning with the work of einstein themselves, it's the paradigm change and now the best that we can do is the probability of what they will be like tomorrow. and that was not an easy transition for the physicists in that era to take on board. it was an emotional upheaval for many of them to make this transition but here's the thing. as sean will describe in detail, the wall of the quantum
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mechanics can be used to make predictions that agree with observations for fantastic accuracy. to nine or ten decimal places and the agreement between theory and experiment is so potent and powerful people begin to stop thinking about what it's telling us about the nature of reality and begin to use it as a wonderful structure to make predictions about the world to begin to control to yield all of the wonderful technological gadgets that we walk away with all the time and infected is more than that. it's got to the point anyone as a physicist that wanted to about the meaning of quantum mechanics, but it was telling us about the world and how it wor works, they were looked at as someone that lost their way. it wasn't something we were
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supposed to do. there are a few people that say that trying to figure out in particular how we transition to the definition of th that we experience and many ideas were put forward. shawn will talk about the most loyal of all the possibility that we are part of a multi-verse, many worlds, parallel universes, the very strange idea but i will say this. ever since the events of november 28, 2016, people have an easier time understanding the concept of parallel universe. and with that it gives me great pleasure to introduce tonight's speaker you all of course know him from his many best-selling
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books on the nature of time, the particle, the nature of reality itself we know and love sean as one of the great pioneers in understanding caused algae and quantum physics tonight you have to treat to hear from one of the profound thinkers that are willing to push into the quantum physics to try to figure out what it's telling us about the nature of reality so please give a warm welcome to my friend and colleague. [applause] thank you secret science club and all of you for figuring out this week for its. i don't know how that happens, but i'm happy that it does. when you become a physics
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professor they teach you that what you teach other people even if it is an abstract concept it is best to do demonstrations to bring it down. i'm going to start by demonstrating. i'm going to push a button on my phone which will send a signal over the internet to a laboratory in switzerland which will send a photon particle and hit and go either left or right with 5050 probability and then depending som, the signal will e back here and tell me whether i should go to the left or the right. here we go. the photon is admitted. that's the demonstration. thank you. why is it worth anything at all
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it's because in my favorite version of the quantum mechanics, which i will tell you about come if predicts and i believe it is true that there is an entire reality where i hopped over there and am currently standing there to my left is a different version of me that did something different and like i said, i believe this is true what you should be saying is that kind of crazy person would believe this is true? but what we are here to figure out and let me see if i can do the technology. >> the reason we are talking about the things it is enormously successful. particle physics and even my chairs and tables to collapse. but as my predecessor tells us i
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think i can safely say nobody understand quantum mechanics. i usually don't like to appeal to authority by bringing up others but the claim i'm making nobody understand something, it's a good authority to say nobody else understands it anyway. how in the world can it be possible that even though he was quantum mechanics to make these predictions with enormous accuracy someone can say please see we don't understand if it's because we can make predictions. they might say i don't know. the fact they would say i don't want to know i just wanted to make predictions, it is a typical attitude and they should be embarrassed with themselves. it wasn't always like this. no one would have said that this
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a hundred years ago. when they came on the scenes people were tempted to think the only reason we do physics is to make reductions and not to understand how nature works. given that we don't understand the quantum mechanics, you would imagine since they are so important, the task of understanding would be the most important thing in all of physics. we have several of the world's leaders in understanding the foundations of quantum mechanics. these people could be millionaires living in an apartment that they are not. they are great people and they are underpaid and undervalued and so it isn't only that we don't understand but that we haven't even tried. i want to highlight the degree of embarrassment a physicist would have and say of the fable
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the fox sees some grea grapes ad hops over but they are too high so he says i didn't want them anyway they are probably sour. in case it isn't perfectly clear the fog present the understanding of quantum mechanics. we used to try but we could do it. starting tonight everyone is going to understand quantum mechanics so i'm going to do a tour of why we came up with in the first place and why it led us to these crazy suppositions that are not a particularly historically accurate torpid history is messy and we don't have time for that so i will tell you the story that gets us there in a relatively brief period of time. 100 years ago or a little bit
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more scientists are putting together the picture of the at atom. there's a nucleus at the center and today we know it is made of protons and neutrons. orbiting around like the planets orbit the sun are these electrons that are successful for various reasons and it also cannot possibly be right. remember also before quantum mechanics came along we had a theory called classical mechanics that had been given by isaac newton and his followers and it makes the prediction when you take an electron, a charged particle and send it around in circles were up and down it emits radio or infrared electromagnetic wave. all that you are seeing comes from an electron so here you
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have them zooming around being accelerated. they should lose energy and what they should do indisputably with classical mechanics is spiral into the sector of the nucleus. the chair you are sitting on, everything in the world, it should collapse. it has zero extent it should collapse into a black hole but it apparently doesn't. scientists have a good theory it was conceptually inadequate and we need to do better. it was hard to do better. there are steps that i'm skipping that they came up with the following ibm maybe it isn't a particle. maybe the way to think about it is as waves and not particles.
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there was a debate about whether it is so someone eventually said that the electron we call it the way that it represents the electron one of the least romantic names of the concept of all of the physics but that is what we call it. it spreads out around the nucleus for this concentrated in the middle and then it fades away and basically you can do the math problem to say what are the different ways that an electron could settle down into an at-home and even though the way that it is all energetic and so forth there are certain discrete shapes that it can have where it has a specific energy to sit there and not change. so the electron settle into this. this is data, this is a picture of an electron around the helium
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where it is located. it's not in the sob simple orbit, it is spread out around what we call the wave function. they are not actually moving. i hope everyone is happy with this but the greek letter represents an electron and on the left you have a question that is asked mainly how much
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energy has been used and on the right, you have an answer which says how fast are you moving so there will be various different parts of the different energies and it simply says high energy cards change rapidly and low-energy prudes change slowly and that is basically the whole story. what matters is that there is an equation. physicists love the questions. some of them don't love them as much but it is full employment both of the scientists in for the students doing homework though he creations as now that i know not just what it's doing that in any circumstance comes up short in the equation is where it is. the scientists got the ability to say how it evolves with time. everything was looking good except for one obvious and huge
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dramatic wall that says when you look at electrons if you are not high-tech and this is a recent picture for the reconstruction based on very delicate stuff, usually when you look at electrons, they don't look like waves, they look like particles. so this is a little chunk of uranium admitting particles in the cloud chamber that we leaves a little string of bubbles behind and it's the result of a charged particle being admitted by the radioactive uranium. what i want you to learn from this picture is the prediction from some radioactivity it is admitted in a spherical.
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that isn't what you see when you look at it you see a particle moving. they have to hope that when he solved the patient he would find that it looks like a particle. then people did actually solve the equation and it spreads out all over the place. there is a dramatic mismatch that says the way they spread out and the observation that says that it looks particle like so people invented the following terrible, awful, no good idea which is that they can be spread out, but when you look at them, they collapse. they are shy. [laughter] so, you think i'm kidding. this is what we teach our students. there's the function all by
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itself and on the right it says when you measure and say where is the electron you don't see that cloud, you see is located in some particular location. there's something that happens when you look at the function. this is what was figured out and this is what people told themselves in 1926, 27 and 28. this came to be codified as luckless mom as the copenhagen quantum mechanics and this is what we teach our students today. if you open up a textbook in the quantum mechanics you will find if you ask it to the functions do, there are two sets of rules. they do one kind of thing when you are not looking at them,
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they obey the equation and if they do another kind of thing when somebody looks at them, they collapse in a particular value and the probability of getting any particular outcome. so it just means the probability of measuring the electron is relatively large and the probability of measuring it out there is relatively small. like i said i am not making this up. i want to say this is utter nonsense but let me be client to be the kind this is unacceptable as a theory to nature. this clearly cannot be the right answer this is why people tell us that we don't understand but quantum mechanics because nobody in their right mind think that this is the ultimate way to the reality works. i will highlight two of the problems with this cookbook that we are given.
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one is what we might call the oncology problem, philosophical, philosophers use the word oncology to talk about what is real, the study of being. what is the world just what do you observe that even when you are not observing it so you notice that we kind of slid around on the western and we were being introduced to the copenhagen. there is a function, but what reality is that? is a one-to-one representation of a complete story of reality were only part of reality a bit of function and other things as well maybe there's particle as well. or the word has nothing to do with reality. maybe it is just a little black box that we can use to make predictions about experimental outcomes. there are people who believe all these things and who do not agree about what reality is according to the quantum mechanics and slightly more publicized is what we call the measurement problem which is
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even more obvious. what do you mean look at. come on, looking at things changes them. do i have to look at it lacks what about something nonliving like a photograph or video camera backs but if i just look at it if i squint and don't forget very carefully doesn't imply that somehow my agency of consciousness and my disembodied mind has something to do with the fundamental recipe of reality? again there are people who believe all these things, i don't want to discount them but at least we don't agree on the answer, so there is a problem. what are we going to do a? i have ideas, that's why we are here. there is a very well-established position highlighting how mysterious and weird and spooky everything is and never telling you how to get it right. when finally there to tell you my favorite version of how to
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get it right. a graduate student in 1957 basically acted as a quantum therapist. what he said was look, you have been working too hard. chill out a little bit. you have some good-looking rules for what is going on. there are functions clearly, they obey the equation a lot of the time, clearly, then the simplest most straightforward thing is that the function is everything. there's nothing else and what it does is obey the equation over time does nothing else. right away he published the pieces and try to convince other people what he thought was interesting and he said no its not. so, there is the interpretation of quantum mechanics. there is one the set of rules applies all the time, no matter
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what is happening and it is exactly parallel to every other theory of physics and every other theory of physics, electromagnetism, general relativity, there are states, positions and momentum were fields and those states are all according to an equation. all this stuff about measurement and nonsense, just erase it, get rid of it, you don't need it. okay it sounds like it is going to be good if it works that stuff about measurement was invented for a good reason. we saw the picture with the particles. we don't seem to see the functions, so how in the world could this simple lean and mean austere version of the quantum mechanics possibly match the data in our experience? the secret is a little feature of quantum mechanics called entanglement which you may have heard of. by putting it into the modern
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terms as brian mentioned by also wrote a book about. i wouldn't be hurt if you took out your phone right now and ordered a book that's okay if you did that. but if is on the will be particle that we've ever detected that has zero spin. a quality that elementary particles can have. it's very much similar in spirit to the ordinary spin of a spinning top of the earth, but it comes with a discrete amount. so the spin is zero isn't spinning at all and it can decay in various ways. it can go to two electrons actually an electron and anti-electron. they do have a spin. they spin one half, but it goes into to particles angular
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momentum is one example, so it must be the case that this benefit to cancel out from each other because it has to add up to zero before, so we talk about this they can either go up or down those are the two choices and electron number one could be up or down. electron number two could be spin up or spin down, but they must be opposite. that is what we know. if any momentum is to be conserved. so, the way that that happened in the quantum mechanics is that it decays into what we call a superposition. there are two possibilities. either electron number one is up or down or electron one is up and down but it's not that we don't know. it's just like the one in electron with it its function
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spread out, that's what the function is. we are taking the point of view that it's everything now. so, what this means is that it decays into the function that is both possibilities at once so we say that they are entangled with each other. we don't know if it is going to beat up or down. we don't know if it is going to be up or down but if we measure the spin of electron number one afterwards, we know that it will be the office said that they have to cancel each other out, so they are related in some way. they are not separate from each other. the lesson here is that in quantum can ask their are not separate states for the individual parts of nature. there are not separate functions for each particle. there's only one function called the universal wave function of
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the universe and it is described as the probability of measuring everything in the world all at once. so, you might think if you were trained on the newtonian classical physics, you might think there is a state for particle number one which is up and down and the state for particle number two is a plus down, but that isn't right. it says there is only one state, the function of the universe and it's a combination of both. that is entanglement. the possible answer that you can get for one particle is related to the other one. so, what does this have to do with measurements like that? to get there, we are going to bring up the thought experiments who put the cat in a box so he says imagine i have a box with a cat inside additives of radioactive sorts like that which we saw before and they can detect when the source emits a particle and there is a quantum mechanical probability that will
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open the box, gas will come out of the box and in the original telling it is poison gas, cyanide and the cat died. and as the doctor once said, i think my father just didn't like him. [laughter] that's really true. i didn't think that one up either. i see no reason to kill the cat. to undo decades of cat killing that had been favored by physicists, so isponsoring my tt experiment, it is sleeping gas. the point of it though is that when he hasn't yet opened up the box, he says look apparently -- by the way, he didn't like any of this. he likes the equation but at the time that he invented it, he didn't have this interpretation of the vacation that you squared it and got the probability of something. once you realize that that is what it's for he wishes he had nothing to do with it.
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he didn't return the nobel prize for. so, he's as according to my equation is the wave function of the radioactive source is a superposition of having them having not, then the function of the superposition of having detected in having not another wave function is in the position of having opened in having not, the function of the cat is in the possession of being awake and being asleep, so his result, his conclusion was this, surely you don't believe that that is what really happened but that is what his own equation said that he used to illustrate the difference and reasoning between the classical physics and quantum mechanics, so i'm going to introduce those. i know that this is everyone's favorite part of the science talk. when i have things in a square brackets that means they are classical somehow they have definite value and if there is) they are quantum so classically, i would say the cat is alive or
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dead, awake or asleep. i might not know which it is. i might be uncertain but there is a fact of the matter is either awake or asleep. quantum mechanics says no, no there is a whole another set of possibilities in the position of being awake or asleep, that is the short and of the equations if you had taken a little bit of quantum mechanics and you were taught the textbook of copenhagen, what you were taught as there are quantum mechanical systems in this case and ruled by the catholic there are classical observers. the observer lives somehow in a classical world, the observer doesn't have a wave function and jusjust observes things and get answers and has definite values and the justification for this is have you ever been in a superposition? no attack was aslee the cat is e
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observers are asleep. i tell you this as a lobbyist because i want to contrast it you can be int in that positiono everything is in parentheses.
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then the observer opens the box it doesn't have anything to do with consciousness it just means i absorbed the equation and i had a physical interaction between what is outside of the box and what's inside the box, obeying the equation at all times. so what does the equation predicts when i opened the box? here's what we know, we know that if we open up the box and the cat was entirely awake, you would see in a week cat. let's agree on that. if the function of the cat was entirely asleep, you would see a sleeping cat and that is all the information that you would need to know exactly what you would observe if the cat was in the superposition, namely the function of the universe evolves into a superposition of the cat was awakened the observers will have to wait, but the cat was asleep into the observers will
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have asleep. literally nobody in the world disagrees the fact that this is the prediction of the equation. they might disagree that you should be using this equation, but that is the prediction. this is why no one believed him because he said he disobeyed at the equation and if you follow that it sounds like i., myself, dissolved the possession and i observe on some things before and never felt i was in a superposition. i didn't feel like i was in a superposition of hopping left in hopping right when i did the experiment. i felt like i thought left and there seemed to be a fact of the matter about that. what's going on. well, i think like every got it right in 1957 but he didn't have the right to get it right, the real reason that it is respectable is the idea that is now coherence which wasn't figured out until the 70s and
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80s but it stems from the same philosophy of how to think about quantum mechanics, namely there is only one-way functio one waye entire universe, then he noticed we didn't include the entire universe here. what about the rest of the universe? technically we should do the rest of the universe in. you might think that doesn't matter. we call for the rest of the university environment. the environment is just a technical term that we used to mean the entire rest of the universe where we are not keeping track of everything that happens, so we are in a room here with light, particles of light, photons, adams and our fuels in the air and so forth. i don't know the position of the philosophy of everyone of the photons. i wouldn't even know if they changed a little bit, so that stumped us all into the environment come into the point is it is both inside and outside the box. there's air and light in the box and outside, so if the cat
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starts out in a superposition of awake and asleep, it interacts with the environment right away. before you open the box, there is a process called being coherence in which the state becomes entangled with the environment so basically the cat and the environment wave function evolve into a superposition of the cat is awake in the environment and the cat is asleep into the environment is whatever it would be then. then you open the box and that is the measurement process and you see and answers for this is the true way function of the universe, slightly colorful depiction, counterweight in environment with the counterweight and then likewise the cat is asleep. why would it matter in the slightest that i keep the environment in their? is because that's what i really
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mean by measurement it's nothing to do with the human beings or the video cameras or earthworm or any semi-conscious creature. the measurement occurs in the scientific physical thing when a quantum system that is in a superposition becomes entangled in the outside world, it becomes entangled with the environment. and when that happens the following wonderful thing happened but if the person and a part of the fun symptoms all the cat awake says is there a whole another universe, is there a whole another part of the function with the cat was asleep, is there an experiment i can do to detect that this, am i affected by the other part of the function, the answer is no because the environment is so dramatically different about this part of the function cannot affect and is not affected by the second part of the function. in other words, just to the
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inevitable movement of the function according to the equation, these two possibilities have become non- interacting with each other. it is as if they become separate worlds. so, as rick says the likes of which, you know what we should do to get more publicity, we should call this the interpretation of quantum mechanics. he originally called the theory of the universal function, but you've got to admit many rules is a better name. so, the problem with this is that it makes you think if you haven't gone to talks like this or read books like mine, the word many worlds interpretation makes you think that i am adding extra worlds to the quantum mechanics to help make sense of it. but at no point did i add world. all i did was force the function to evil according to the equation. they were always there.
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as another physicist once put it, every other formulation of quantum can ask is a disappearing formulation of quantum mechanics. all efforts wants to do is say the world is there and that's okay. that is the therapeutic food. now, there are many questions and again i would refer you to this excellent book that just came out, but there are questions about the details of the quantum mechanics like how many worlds are there. well, there are lots. that's really all i can say. they are really well could be an infinite number. the truth is we don't know because that is part of the embarrassment that we haven't been for the last several decades doing the work we should be doing trying to understand quantum mechanics. we've left questions the car are an infinite number, go by the wayside. at one way or another there are many of them. and in the way i want you to think about the world and the branching is time is coming from
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the bottom to the top. when this branch process happens it's not double the universe because then people get worried about questions like energy conservation, like where does all of the energy come from. it's really much more like there is an existing amount, and it gets subdivided. so, i called in the book the wake of the universe, which is just the function squared in total, that seems the same according to this equation. it remains the same amount, but it is branching off in the universe splits. the individual branches become thinner and thinner. so, this answers the question that you might have if i know of and eveready and and also utilitarian, so i want the greatest good for the greatest number. should i suspend all of my waking days splitting us to create mor our people thereforee happiness lacks no. shouldn't do that, because that would be balanced by the fact you are making it thinner and
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thinner. so, think of the universe splitting and it's happening so often, happening so frequently every time and add him decays, like when that act radioactively decays inside your body, roughly 5,000 times a second. so, that isn't in every second you make 5,000 more universes. every 5,000 times a second you split the universe and two, so you make to to the power 5,000 universe. every second just in your body and that is a lower limit because every atom in your body that doesn't decay also contributes to the splitting of the universe because there is another in which it did so rather than individual discrete events when it branches of think of it as an ongoing constant process of the universe is just splitting of the splitting and differentiating. but don't worry, there's plenty of room for all. there's matthew can do to
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convince yourself of that. that isn't what i want to talk about here. i want to go over some of the prospects, the good news, and that is basically once we start thinking about it a little but carefully, it helps us maybe answer other questions that we have been puzzling with for a long time. let me get some objections out of the way very quickly. here is a bad objection. that's too many. [laughter] where can we fit them all. i already answered that. there is the same amount of quantum mechanical stuff in many worlds interpretation and every other interpretation. there's room in the space of all possible ways function for a very large number. don't worry. if you believe superpositions are real, there's plenty of room to be in the superposition of many different possibilities. the only question is whether you let those describe reality. you might also worry that it can't be tested. i can't see any of these other
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universes. if you read even a small amount of the philosophy of science, scientists, bless their hearts, have ever only read part of this philosophy and if they read it it is carl popper and they haven't read it but they've read he once said that to make a scientific theory it needs to be falsifiable. that is to say in principle i could imagine an experiment that if i got a certain outcome coming in experiments with show me that the theory was wrong. not that it is wrong or false, but in principle it is falsifiable. if the theory isn't falsifiable, then it isn't science. we know better now. there are a good set of details he did get right, but even at that level it isn't an objection to the ever ready quantum mechanics. you might say wait a minute. i can't falsify the existence of all these other universes. but remember, the point is not
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the other universes. they are a prediction of the theory. they are not input to the theory. the input is there are functions in the equation in order to falsify the many worlds interpretation. all you have to do is show a function and contradiction to this equation, even though it isn't entangled with anything else. there are ongoing experiments to do this. there are other alternatives to the many worlds to predict that there are different physical consequences. in fact, one of the interpretations was karl popper. she saw that the copenhagen interpretation was a monstrosity and was shocked that a physicist with take it seriously. he did have one of the many worlds interpretation because he had his own that didn't g it dio very far but as far as the scientific ability is concerned, the ever ready quantum mechanics are testable as you want the theory to be. now here i want to emphasize that as much as i like the many worlds interpretation, we are
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not done. we haven't done the work that we need to do. there are perfectly good grace to have that many worlds might not be right. happily, secret science thought it needed six hours, wait until you got all the other interpretations of quantum mechanics. i can't do that, i will tell you what the worries are about the many worlds. my favorite, there are two of them that are my favorite, i love them equally. one is why do we get probability in this theory at all facts in the copenhagen interpretation, there is when you observe the collapse of the probability being put in, everett just says there is an equation and that is deterministic. deterministic. deterministic. there is nothing probabilistic about it. if you give it one time, i know the quantum base of the universe or the other times. why is there any talk of the probability of getting a certain
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outcome for different measurements? and the other one is how does the classical world emerge? this i think is also more interesting and an important problem, but it's one that very few people have paid attention to, because we cheat our way around. we sort of within a classical world we've put it in by hand and i think we need to do better and by doing better and can actually learn something. let me rush through questions and then chat a little bit of question number two part of the answer is because many worlds are purposefully deterministic. whatever the probability is, it isn't a truly chancy element of the dynamic of the theory. it has to be what the philosophers call systemic, it has to be our ignorance is somehow causing us to use the probability talk. you might say well if i knew the exact function, i know everything. and bear you are wrong.
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that is the wonder of the many worlds interpretation even if you know the function, there might be something that you don't know and therefore you have to assign a probability, and that is where you are in for a function. so, remember the story be told where you have the cast, superposition, environment, observer the first step was coherent and entangled in the environment. it becomes entangled. they become entangled in the environment but the observer has not yet become a. so i can still treat it as two different branches of the function but also a it doesn't know what branch of a rrs with her are now to. neither one of them know what branch there are.
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if the probability of the function square. now again not everyone agrees. those people are wrong but that's okay. the problem that i think is richer in some sense and unless involved in the probability issue is finding the classical world. so, this is one of the things where i first needs to convince you there is a problem and then that we are making progress towards solving it. chairs, tables, it is all around us. but you have to find it and that is because it is very natural as
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human beings to think about the world classically even human beings who take quantum mechanics course is if you are out there hunting lions or whatever, maybe it is spread out in the probability you are going to be evolutionary selected away from the gene pool. so as a result, we tend to privilege what we see. so we start with leaves of grass and people. and in the physics literature we do -- we have a classical system with a set of rules that physicists can apply an essay i want to invent a wave function of the electromagnetic field or whatever and mathematically that function as an element of a
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state that i drew here. really it is a bit chilly in -- bajillion. presumably, nature doesn't. reality doesn't start with a classical system and then quantifies it. it is an quantum from the start. we should think about it if we are emulating how nature works to start with the quantum system and a say in certain circumstances under the right conditions there is a good story that we can tell which we call the classical mechanics so that we should be able to do at the start is with a mathematical object think about its doing and how it's evolving, but the dynamics are and then say that is a cat that is a person, but as a leaf, etc..
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this is hard and no one thinks about it so we are just at the beginning of the past. i think we can see a way forward. most of the work is being done by the idea of locality, the idea that space, the three-dimensional space that we live in is so special it evolves and things bump into each other where they are at the same location in space. there is no real action at the distance as einstein says. if you want to actually communicate, you send a signal place by place you can't teleport things back by the speed of light. why is this important? think about the cat. think about why when you open the box you see the cat is awake or asleep. after all these are just quantum states, there is a perfectly good quantum state of the form a week plus a sleep. there's another state awake
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minus asleep and all the different combinations. when we opened the box we only ever see awake or asleep. these are the preferred states of the cat. why is that? remembered the way the function branches the box bumps into the cab and what do they bump into? different photons bump into the cat differently so the asleep cat on the ground and the awake cat trying to get out. here is a picture of a photon that would hit the cat were it a week but would miss it if it were a sleep. the reason why it branches is the systems of definite physical location and that's because that is how the interactions were. they pick out locations in the world. so, even if i handed you an abstract function and said what
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is it so you can imagine building up the concept of space space is a prerequisite, the actors of the world layout on it and in this advanced ever ready in from al-isam we will have to find and space so rather than saying interactions are local in the space what we will be thinking is it a set of variables and let's see if we can move progress on this. the other thing we know is that
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it is curved. professor einstein taught us this. even if it is a stage it is one of these modern stages of moving parts. they are curved and heal that curvature into orbit around the sun and whatever other things people do the problem is a gravity is the one part of the current understanding of the
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fundamental law of physics that we haven't made fully quantum mechanical. everything else for electricity, magnetism, electrons and so forth it seems to work to the arbitrary factors. gravity works for the ne the mon living around the earth, but not in important cases like black holes or the big bang or anything like that. so my feeling is the reason why we haven't been able to find the quantum theory and gravity is because they keep starting with the classical theory and i think that is a mistake. i think rather than, we should try to find the gravity within the quantum mechanics. in other words, why in the world should we be surprised we don't understand the quantum gravity that we don't understand quantum mechanics. maybe we just got lucky and we were misled by the fact we could
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find quantum theories of the magnetism and so forth. how in the world are we going to do that? it's not that we are moving completely blind. we need to get a hint of what we know works. it is our best current understanding of the one gravitational, the magnetism says it isn't even particles that were ever quantized. and what you think of it as a particle is just a place where the field is a little bit more energetic than you thought it is. so in the particle point of view, you might think that there's empty space and literally nothing is happening. but where there are particles, something is happening. it says something is happening everywhere even in empty spaces there are fields of migrating. we can precisely characterize them in a certain way and if you
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take one of them and move it forward looks like a particle fury so the same story in these experimental predictions that is a different way of looking at the world. and guess what, these little regions about this they are entangled with each other. of course they are. entanglement is everywhere in the quantum mechanics. so even if we call the vacuum there's literally nothing there. it's empty but there is still a quantum field entangled with each other and the kind of obvious way in the nearby region in space they are highly entangled with each other. we don't know the space and the distant. maybe we can define the distane
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using entanglement and it is a feature in its own right with no reliance on the classical conception. it is a pre-existing conception so maybe we can say when the regions are on the entangled with each other they are far away but they are very close by when they are very entangled they are close by. if you can imagine doing that for those that make up the function you would find an entire geometry on this emerging space. if i know the distance between any two points in space and either the sides of the triangle, i know the geometry of space. that is what einstein wants us to talk about. so, i claimcoming into this isn't somethinand this isn'tsomd that we know is true, it is a hypothesis that we are exploring
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the consequences of. let's imagine we could extract geometry from entanglement. there is something that we do know for sure that it is related to entropy. when the two systems are entangled with each other, either one of them separately you can very roughly think of it as how much you don't know about the state of assistance if they are to be entangled neither one of them is in one quantum state all by itself. it's not true that we don't know if this kind of like an analogy that it's a formula when they are entangled to quantify the amount of entanglement by the entropy of the different substances.
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finally, there is a relationship between entropy and energy. remember i said that the particles of the quantum field theory he picked up a little vibrating quantum field theory and you've also broken the amount of entanglement between that little quantum field and the rest of the field without you. so you decrease the entanglement and increase the entropy and increase the energy in that region. there's another equation i won't show you that there is a mathematical relationship to the amount of entanglement in the region and quantum field theory and the amount of energy in the region. i know that these are all going to die but here's what we learned. there is a relationship between geometry and entanglement because we think that it would be cool but somehow the state emerged from the features of the quantum function. there is a relationship between entanglement because they said so and the nation enter in the a
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relationship between energy and entropy we can divide and the circumstances in something close to the quantum field theory. therefore, it's the relationship between the geometry of the space and the energy in it. that is from the general relativity course. that is simply what einstein says when he invented the theory of general relativity. it is governed by the amount of energy in that region broadly construed. there is more than that it just means greek letters and so forth a general relativity, but the moral of the equation is the more energy you have in the region, the more that it occurs the space-time around it. ..
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>> my advice is. [laughter] that if my goal was to make you perfectly understand this i would be crazy because nobody perfectly understands that. but physicists have been making mistakes over the last century trying to understand quantum mechanics and my
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particular strategy but whatever you do for a living stop doing that and start trying to figure out quantum mechanics and where that comes from. [laughter] so we are trying to think in new ways that may or may not work but it is our responsibility to figure these things out. this is as understanding how nature works and that's what i think we are doing. thank you very much. [applause]
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books are for sale and now we will take your questions. >> hello. the most agreed-upon theory predicts. >> know but keep going. >> my question was of the many world interpretation of quantum mechanics make it worse because now those quantum states quick. >> yes. so if you don't hang out on the street corner it is the
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high-tech equivalent of a box of gas that last for ever basically it stays spread out with equilibrium. but then moving around in random patterns if we wait long enough they all moved to one side of the room or they make a little brain. so the universe would like that number one made of tiny pieces and lasted literally forever over the course of eternity turned into planets and people and minimal thing is enough fluctuation that was is conscious enough to go at
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the space and then it's done. and the question is if there are so many more than how can it be right? but the short answer is most say therefore one of the hypothesis is wrong. and comes down to the true status so the guidelines of those theories of random fluctuation and then throw that out. it doesn't make the problem any worse. it's not the idea of everything but there are plenty of things that don't happen and even more that happen very very rarely.
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so if all the predictable - - predictions were little in this world with a single universe theory. >> it seems to be you have a conservation level of embarrassment but it seems hard to believe so wouldn't it be easier just to not let go and those that are superseded by relativity? with less embarrassing explanations quick. >> yes. be my guest. [laughter] the short answer is everyone in the world of quantum
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mechanics today. i have accepted they are there. but it turns out another theory is harmed forgot that's okay. don't worry about it. everything will be fine. [laughter] >> if geometry is emerging with the culture.
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>> but if i had more time i would be more careful about this but when they are more entangled of culture of those quantum fields but it's not a story of particles. want to have two particles they can be equally entangled no matter how close or far away they are but it is overwhelmingly dominated but that is interesting so then
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you have this whole conversation of the entanglement of the emerging geometry of space time with particles on top of that the bad news is it doesn't help with any feelings you may have. >> you mentioned to be consistent with conservation and energy what property are you referring to quick. >> i can tell you that. some believe the copenhagen interpretation it is the way functions squared that philosophy over heavy possible outcome that is the thickness of the branch so when you go into two different possibilities square root over to then you split one into two and so forth so that is the
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equation according to schroeder's. >> in quantum mechanics is there a depth to the universe quick. >> sure. it will happen. most of the traditional friction - - predictions through quantum mechanics is relevant to the previous question we live in a universe not only expanding but accelerating emptying out at the rate we think will never go away. the best current theory we have we have 14 billion years in the past infinity years in the future all of which that the universe will settle down
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and then sit there quietly forever with no living beings around then only 15 years before the last star burns out. >> i'm wondering of the wagner interpretation and broader with the role of quantum physics. >> so when i mentioned if consciousness is part of it the interpretation of quantum mechanics we think there's something special when you observe or measure and a nobel
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prize-winning physicist you come to that conclusion may be this is crucial to understand quantum mechanics. part of this is an old joke that it comes from the fact nobody understands quantum mechanics or consciousness. then they tried to make it more respectable than that but he was wrong and said that's a bad idea so stop many more people suggested that emily said no. so there are still people who draw a connection. is not the craziest thing in the world with a lack of understanding but i think there is zero evidence. because consciousness is complicated.
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>> do you entertain any simulation theories and the nature of quantum mechanics that you could conserve a large amount of information with that possibility we are getting better and better with artificial intelligence. you can imagine computers are so good they are artificially conscious creatures in the computers not knowing that we exist they talk to each other and live their lives all the possible criteria then you say maybe that is me. maybe i'm a little creature in somebody else's computer and
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that they are a simulation. i don't buy that progressing to the extent you would have predictions for what the universe would look like those predictions do not come true but it is possible and i'm open to the possibility of it but my personal feeling it has zero to do with quantum mechanics. if i were simulating it would make them classical. the information you can keep with all these entanglements is enormously bigger. that's why quantum computers may be much more powerful than classical computers if you're only criterion was to save and i would not do that at all.
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>> thank you for the talk. you mentioned the measurements and where we find that classical world. i do a lot of statistics so i'm trying to understand with respect to the measurement problem if we do something simple like a survey we don't consider that controversial that's just the point estimate we don't think of thousands of other worlds so why is that the incorrect analogy? into the second point of the classical world with the concentration of measured phenomenon so maybe the classical world is infinite
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and that's why it appears so stable. >> that's a very natural way to go and that's what i said was thinking in the twenties but it doesn't work in the easiest way to see that is the probability of getting an outcome its way functions squared. the way function could be negative and could be complex and work with the probabilities. because the way function can interfere with itself different parts can add up constructively or destructively. with the numbers that are not negative and the reason they don't interfere with each other. that's a first clue is not the way to get the probability distribution but it is real in
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some sense that's my answer. >> i have a question so you say you really think that things are splitting off. so do you visualize with your own life there are other versions of your life taking place and what the impact is? or contributing to your ideas or is that something that could freak people out or make their lives better? if they gained more cultural traction was the impact
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quick. >> freaking people out is a feature. [laughter] what we're trying to do is understand reality at the most foundational element what we have been trained on is a tiny insignificant sliver of reality we have been expanding our view of reality and then it becomes weirder and weirder. because it comes further away from our everyday experiences. so the fact of quantum mechanics with something that is so weird and seeking out i think that is good nevertheless this is the best the simplest theory but of
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course when i was a kid what creeped me out is what if the universe never existed? that's what would keep me up at night i didn't know the answer but there are others but it's hard to get it right and come up with the exact way to think about these things existentially i can't talk to those people in fact it's almost a theorem of how you should live your life with this view of reality is exactly the same with the copenhagen interpretation. >> we have a centrist back here. >> i didn't know there were any. >> so with the concept of
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space how would you use that construct as time quick. >> that's a whole other lecture but you did catch me. very good the curvature of space time are two different aspects but the thing that i talked about was really space. so there are ways you can get time to emerge and then you have entanglements what if it was fundamental and not real but what that means that there is some system of the universe that has the property that it acts like a clock depending on what the subsystem is doing it's doing what the rest of the universe is doing in such a way the rest is evolving with time.
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so it can be done but is not necessary although it's entirely possible deep down space and time are one another with that manifold that is a phenomenon. so this is the kind of thing we should figured out 50 years ago but we are just tackling it right now. >> he will be signing copies in the back and you can talk to him there. thank you sean. hopefully he will be back to talk again next time. [applause]
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mental and physical health. >> all right. good evening everyone. thank you for supporting your >> good evening everyone thank you for supporting your local independent bookstore. please make sure all phones are on silent also other events this month reading from
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